Improvement in bridges



FREDERICK SMITH, OF "'BALTIMORE; MARYLAND.,

` Letters Patent o. 75,477, dated Zlfmc'i 10,187'68,

IMPRQVEMBNTIN namens.-

fotti tigitnieniet-ttt "it it time @titten atent mit' mating part oftigt tame.

To] ALL WHoMLrT MAY ooNoEnN: v v t fBe lit known that I,'F1 tEDERIcK'H.SMITH, oi' Baltimore, inthe county of Baltimore, and State ofMaryland,-hai'e invented ane'w'an-d@ble-Improvement inlBi'idges; and dohereby declare that the following is a 4full, clear, and exactdescription thereof`, which will enable others skilled in the artto makeand use the saine,

reference beinghad tothe accompanying drawings, forming part of thisspecilication: Figui-e 1 is a side elevation of ny improved bridge.

4Figure 2 is a crosssection of the same. Y 1 VFigure 3 is a trip viewof. a portionfof the same. Figure 4 represents a portion of thebottomchord, the superstructure' being removed.

Similar letters of refereucer'indicate corresponding parts. Myinvention'has foritsohject to improve the construction of bridgesfsothat any desired. part of the bottom-chord can bc readily adjusted,tao-tighten or loosen any desired part of the bridge, or to allow anydesired part ofthe woodwork to be removed and replaced; and it consistsin the construction and arrangement of the bottom-chord, as hereinaftermore fully described. I

In-the drawings, my .im'p'io'vedbottom-chord -is represented as appliedto a 'Howe truss, but it is equally applicable to any other form"of"beam-t russ; y f Y A are the abutments, upon which the ends Nof thebridge rest. B arethe angle-blocks, the upper sides ofwhich, excepttliebloeks that'rest upon the abutments,are made with twqinclined facesto support the lower ends ofthe inclined braces, C,-the inclination ofsaid faces being such that they may be at right angles to the axis oi'said braces. lEach lineof angle-blocks is connected byclusters of rods,D. The ends of therods D pass through nut-platcs,-E, have screw-threadscut upon them, and' areadjustably secured in place by nuts F. The partsof. the'rodsD, and Aall othenl rods in. the structure which havescrew-threads cut upon them, are enlarged, so that cutting vthescrew-threads may notv diminish the strength of said rods. Gr are rods,which 4have"acreiv-threads cut upon them, which pass through theangle-blocks B, and screw into the central partsof` the nut-plates E,and'whichar'of such asizethatthe'areaof their cross-section shall equalthe'unitedare'as of the cross-section of all the rods'in'the cluster,so'that the clusters may be talren through the angle-blocks withoutweakening the chord.` H are nuts, placed upon'xthe rods G, one upon eachside of the angleblock, so` that by screwing these nutsin one or-otherr'direction, any desired part of 'the bridge may beloosened to allow ithe timbers of said part to be removed and replaced when desired.V l iBy screwing the nuts H backwards and forwards, the diagonal lines ofbraces in the panels are length ened or shortened, and the material ofthe braces being incompressible, the action of the said nuts, H, resultsin an upward or downward motion of the top,chord, thu s adjusting thebridge to any desired upward curve or arch.4 'The resistance to beoverconein this operation ofadjusting the bridge as thetimber seasons,:is less upon the horizontal line of each panel than upon thevertical line of'each panel in all cases where the length of panel isless thanthe height, and therefrcthis adjustment can be moreeasily madeby the nuts H, acting in the horizontal lino, as proposed, thanby meanso i' the vertical rods as at. present performed in bridges as vcleanlybuilt; v

vThe drawings represent eaclioluster of'rods,-D, as being formed of fourrodsybut the number of rodsiu cach cluster is immaterial, and mustdepend upon the strain `to whichthe bridge isexpe'cted to be subjected.The number of lines of-clusters in the bottoni-chord is also immaterial,and must depend upon y the required. `strength `of the bridge, one, two,three, or more lines being used,` as may be'thought necessary. I arevertical rods, that pass through the angle-blocks. B, through theangle-blocks J', against which thc upper endsof the inclined braccs,'(l, rest, through the beams K, 'that support the roadway, and whichjare Isecured in place bynutsZ Escrowed upon their upper and lower ends. Thelines o f clustcrs'voi'. rods, D, tha-t form thcbottom-chord-fof, thebridgc'are connected by horizontal cross-rods,-M, whichl pass throughthe angleblocks B, and are sccuredinplace bynuts screwed upontheir-'ends I claim asl new, and desire to secure`by Letters Patent Abottom-chord, formed of olusters of rods oonnected, as dsoribed, in theAponeis, and cojmlecteflfo each other, through the brac'eblocks, by a.single rod, substantially as', and for. the purpose specified.

2. The'corbina'ton of the oiusrters of rods D, uut-plates E, singlerods'G, angie-Hooks B, and nuts H- with eae'n other, with the horizontalcross-rods M, by which the various lines of clusters ureconuected`-toeach other,

und with the vertical rod 1, by which the bottom-hori und superstructureof the bridge are connected together,`

substau-tially as herein shown and described, and for the purpose setforth. Y

, FREDERICK H., SMITH.

-Wituervsezs:

N. SpGARDNm, H. 0. HEUs'rIs.

